Edge sensing arrangement

ABSTRACT

The invention relates to an arrangement in connection with a wire guide roll of a paper machine. The arrangement comprises a wire guide roll which is arranged to guide a wire, if the wire is driven to the side from its normal track of travel. The wire guide roll is turned in the direction of travel of the wire by means of at least one actuator. The lateral position of the wire is observed by means of a guide flap monitoring the movement of the wire edge, from which guide flap the guidance information is transmitted to a control unit Which, for its part, controls said actuator. Furthermore, at least one sensor is arranged in connection with the guide flap to determine the position of the guide flap and to control the lateral exceedings of the wire.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Continuation of International ApplicationPCT/FI00/00813 filed Sep. 22, 2000, which designated the U.S. and waspublished under PCT Article 21(2) in English, and which is herebyincorporated herein in its entirety by reference.

FIELD OF THE INVENTION

[0002] The invention relates to an arrangement in connection with a wireguide roll of a paper machine, which arrangement comprises a wire guideroll transverse to the direction of travel of a wire, the wire guideroll being arranged to be turned in the direction of travel of the wireby means of at least one actuator, and which arrangement comprises aguide flap arranged against the wire edge and adapted to observe thelateral position of the wire, and in which arrangement the wire guideroll is arranged to turn and guide the wire on the basis of informationprovided by the guide flap on the lateral position of the wire and whicharrangement further comprises means that are arranged to inform acontrol system of the paper machine of the lateral position of the wire.

BACKGROUND OF THE INVENTION

[0003] Various wires are used in paper machines for conveying andsupporting a fiber web. In this connection, a paper machine can also beunderstood as a board machine, a pulp washing apparatus and similarpaper manufacturing equipment provided with wires. When a wire is passedaround and supported by different rolls in a paper machine, the wire maybe driven to either edge in its direction of travel, which makes thewire edge rub against the structures of the paper machine. The wire doesnot naturally withstand this kind of strain, but will be damaged. Thewire itself can be the reason why the wire is driven to the side, butusually this is caused by erroneous positions of rolls. Also impuritiesadhered to the rolls and the wire may cause the wire to move in thelateral direction. To solve the problem ‘a wire guide roll’, whichprevents the wire from drifting in the lateral direction, is arranged inconnection with wire circulation. When the wire is driven to the side,the wire guide roll is automatically turned to the required direction,and the wire is guided back to its right track of travel. The guide rollreceives the guidance information from a guide flap which continuouslymonitors the edge of the wire. In addition to the guide flap, papermachines generally have edge flaps at both edges of the wire, whichsense the lateral position of the wire and give an alarm to the controlsystem of the paper machine, if the wire is for some reason driven tooclose to the edge. A prior art solution is described later in FIG. 1 andin its description. A drawback of the known solution is, however, thatarranging the equipment into a paper machine is laborious. It isdifficult to arrange several flaps, fasteners of the flaps and cablesleading to the flaps to narrow places with demanding conditions. Inaddition, maintenance is difficult, since the sensors are located ondifferent sides of the paper machine and far away from each other. Somemass washing apparatuses apply a thin single-layer wire, and when theknown solution is employed, the problem has arisen that the guide flapbends the thin wire from its edge, and as a result of the bent edge theedge flaps provide the control system of the paper machine with wronginformation and the operation of the flaps is also otherwise unreliable.In addition, since the guide flap and the edge flaps are at a distancefrom the guide roll in the direction of travel of the wire, delays occurin the wire adjustment and control. It is also expensive to manufacturethe solution, since it comprises a lot of various components.

[0004] Furthermore, solutions are known, in which optical sensors orpressurized air streams are used in sensing the position of the wire.The problem of such solutions is, however, that the sensors become dirtyand faulty under severe conditions and, compared to mechanicallyperformed monitoring, the operation is also otherwise unreliable. Theuse of inductive sensors has also been tested, but similar problems havecome up in connection with them as well. The solution further requiresthat a metal strip or the like, which the inductive sensor detects, isarranged to the wire edge. This kind of a wire is, however, expensive.

BRIEF DESCRIPTION OF THE INVENTION

[0005] It is an object of the invention to provide an arrangement bywhich prior art problems can be avoided.

[0006] The arrangement of the invention is characterized in that atleast one sensor is arranged in connection with the guide flap and thatthe information on the lateral position of the wire is adapted to betransmitted from the sensor to the control system of the paper machine.

[0007] The essential idea of the invention is that the guide flap isarranged to observe the edge of the wire in continuous contact and, incase the wire is driven to the side, give guidance information to thecontrol unit controlling the actuator, whereupon the wire guide roll ismade to turn and the wire is guided back to its right lateral position.Further, means for transmitting information on the lateral overtravel ofthe wire to the control system or the like of the paper machine arearranged in connection with the guide flap. The guide flap is arrangedafter the guide roll, into its immediate proximity, in the direction oftravel of the wire, and the devices that monitor and control the lateralposition of the wire form an entity. Furthermore, an essential idea of apreferred embodiment of the invention is that there are limit switchesor corresponding sensors at the guide flap arm, which determine thelateral position of the wire. This way it is also possible to registerthe cases where the wire exceeds the allowable predetermined operatingrange. The essential idea of another preferred embodiment of theinvention is that there are sensors at the guide flap, whichcontinuously observe the lateral position of the wire and transmitinformation on the lateral position of the wire to the control system ofthe paper machine.

[0008] The invention provides the advantage that no separate edge flapsare required at both edges of the wire, but the wire position is onlyobserved by means of the guide flap. Sensors observing the wire edge arearranged at the guide flap. Thus, edge flaps need not be manufacturedand installed at all. The structure of the system becomes simpler andthe maintenance much easier. The solution also enables the use of thinwires, which are cheaper and easier to run. In addition, since the guideflap is located near the guide roll, the wire at the guide flap is wellsupported by the guide roll, and therefore the thin wires no longer tendto bend because of the guide flap either. Thus, the wire edge can beobserved accurately and reliably. The arrangement of the inventionfurther allows the wire to be run looser as before, which makes thewires to last longer in use. When the guide flap is arranged inconnection with the guide roll, no harmful delays occur in the controlsystem.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention will be described in greater detail in the attacheddrawings, in which

[0010]FIG. 1 is a top view of a prior art arrangement,

[0011]FIG. 2 is a schematic side view of a solution of the invention,

[0012]FIG. 3 schematically shows a detail of a solution of theinvention, and

[0013]FIG. 4 schematically shows a detail of another solution of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0014]FIG. 1 is a top view of a prior art arrangement for controllingthe lateral position of a wire. A wire 1 is run in the direction A. Forvarious reasons the wire may be driven to the side in the direction Btransverse to the direction of travel of the wire. The position of thewire in the lateral direction B is sensed by means of a guide flap 2which is arranged after a guide roll 3 in the direction of travel of thewire. The guide flap is in continuous contact with the wire edge. Aguide flap, or ‘a spoon’, is a plate-like element, usually bent to beslightly curved, which is pushed by means of a spring, for example,against the edge of the wire. Guidance information is transmitted fromthe guide flap to a control unit 4 which controls an actuator 5operating the guide roll. The actuator is typically a pneumatic bellows,and the pressure that is fed to it is regulated by means of an aircontrol valve of the control unit. Usually the guide flap is directlyarranged to mechanically use the air control valve. Based on theguidance information obtained from the guide flap, the actuator movesone end of the guide roll in the longitudinal direction C of the wire.Since the other end of the guide roll is arranged pivotally to theframe, the actuator makes the guide roll turn. On the other side of theguide roll there is another pneumatic bellows 8, to which constantpressure is fed. Thus the direction of movement of the guide roll isdetermined by the interrelation of the pressures to be fed to the firstand the second bellows. The known arrangement further comprises edgeflaps 6 and 7 which are arranged at both sides of the wire and give analarm if the wire comes into contact with the flaps. The alarm thatindicates the exceedings of the edge zone is transmitted to the controlsystem 15 of the paper machine. Thus the edge flaps and the guide flapin connection with the wire guidance are entirely separate units fromeach other, and moreover, they are complicatedly arranged at aconsiderable distance from each other.

[0015]FIG. 2 shows a simplified view of an arrangement of the invention,as seen from the movable end of a wire guide roll. A wire 1 is arrangedto move in the direction A via a guide roll 3 which, to make theguidance more effective, is arranged to be elevated such that the wirebends slightly at the guide roll. The end of the guide roll is supportedby a bearing support 9, which is pivoted to a frame 11 by means of slideblocks 10 or rollers, for example, whereupon it can be moved in thedirection C. The guide roll end is turned by means of actuators 5 and 8.The actuators are preferably pneumatic bellows as shown in the figure,but also pneumatic and hydraulic cylinders, electric motors and otherdevices that are suitable for this purpose can be used. Although thefigure shows two different actuators arranged at opposite sides of theguide roll, the guide roll can also be used by only one actuator thatcan be moved in two directions, or the return motion can be performed bymeans of a spring element, for instance. The guide roll can also bemoved from its both ends, but usually this is not necessary. Accordingto the idea of the invention, a guide flap 2 is arranged into immediateproximity of the guide roll. The guide flap is then so close to theguide roll that the wire edges are still firm, due to the supportingeffect caused by the nearby guide roll. Preferably the guide roll,control unit and guide flap form an entity, to which it is easy toinstall the required cables, pipes etc. and which can be serviced viaone service lid, if necessary. An air-pressure duct leading to an aircontrol valve 4 is marked with a line of dots and dashes 16 in thefigure, a channel leading to the first actuator with a line of dots anddashes 17 and a channel to be led to the second actuator, intended fortransmitting constant pressure, with a line 18. A conductor leading tothe control unit of the paper machine is marked with a broken line 19.

[0016]FIG. 3 shows a detail of an arrangement of the invention. A guideflap 2 is arranged to the free end of an arm 12, whereby the lateralmovement of a wire 1 turns the arm in respect to the pivot point of thearm. The arm is combined with the air control valve of a control unit 4such that the movement of the arm opens and closes the connection from acompressed air source to a pneumatic bellows 5 according to the lateralposition of the wire. The allowable transversal range of movement of thewire is marked with a reference L in the figure. The exceeding of theallowable range of movement is controlled for example by means of edgesensors 13 and 14 arranged to give an alarm to a control system 15 ofthe paper machine. The edge sensors can be limit switches, inductivesensors or the like which are arranged to be activated when the arm 12moves to a certain extent. The relative position of the edge sensors canbe adjusted, and thus the size of the allowable operating range can bechanged.

[0017] In addition, one or more sensors 20 measuring the position of theguide flap can be used, and the measuring result is transmitted to thecontrol system 15 of the paper machine. In this case the lateralposition of the wire can be continuously measured during the operationof the paper machine. Such an application is shown in FIG. 4. Valuescorresponding to the allowable range of movement can be programmed inthe control system/automation system of the paper machine. Theinformation on the exceedings of the allowable range of operation L andthe position of the wire can be utilized in the maintenance, when theconditions of the wire and wire guide roll are evaluated and furtherwhen the operating parameters of the paper machine are adjusted. It canalso be seen from FIG. 4 that the guide flap can also be arranged to bemoved linearly in the direction B by means of a suitable slidemechanism, for instance.

[0018] In this application, a control system of a paper machine isunderstood as various automation systems, a user interface and, in itssimplest, a control panel of a paper machine. A control unit, for itspart, can in its simplest be an air distributor with a mechanically orelectrically operated control valve for controlling the pneumaticactuator. The control unit may also be a programmable logic controllingthe electric motor, for instance, or some other suitable controllerbetween the actuator and the guide flap.

[0019] The drawings and the related description are only intended toillustrated the idea of the invention. The details of the invention mayvary within the scope of the claims. Consequently, besides a plate-likeflap, the guide flap refers to other elements which can be applied tothe monitoring of the position of the wire edge and arranged intophysical contact with the wire edge.

That which is claimed:
 1. An arrangement in connection with a wire guideroll of a paper machine, which arrangement comprises a wire guide rolltransverse to the direction of travel of a wire, the wire guide rollbeing arranged to be turned in the direction of travel of the wire bymeans of at least one actuator, and which arrangement comprises a guideflap arranged against the wire edge and adapted to observe the lateralposition of the wire, and in which arrangement the wire guide roll isarranged to turn and guide the wire on the basis of information providedby the guide flap on the lateral position of the wire and whicharrangement further comprises means that are arranged to inform acontrol system of the paper machine of the lateral position of the wire,wherein at least one sensor is arranged in connection with the guideflap and that the information on the lateral position of the wire isadapted to be transmitted from the sensor to the control system of thepaper machine.
 2. An arrangement as claimed in claim 1, wherein theguide flap is arranged to the free end of an arm that is arrangedpivotally, that the arm is arranged to pivot according to the lateralposition of the wire and that the arrangement comprises at least onesensor arranged in connection with the arm, whereby the lateral movementof the guide flap and thereby that of the wire are arranged to bedetermined by means of said sensor.
 3. An arrangement as claimed inclaim 2, wherein a first and a second sensor are arranged in thedirection of movement of the arm to different sides of the arm at adistance from each other, this distance being arranged to determine theallowable lateral operating range of the wire.
 4. An arrangement asclaimed in claim 3, wherein the relative position of the sensors isadjustable, whereby the size of the allowable operating range is alsoadjustable.
 5. An arrangement as claimed in any one of the precedingclaims, wherein the sensors are limit switches.
 6. An arrangement asclaimed in claim 1, wherein the sensor is arranged to measure theposition of the guide flap and thereby transmit the measuringinformation on the lateral position of the wire to the control system ofthe paper machine.
 7. An arrangement as claimed in claim 1, wherein theguide flap is arranged in connection with the guide roll, into itsimmediate proximity, so that due to the nearby guide roll the wire edgesare still firm at the guide flap.